I didn't like the inverted mason jar feeders as they drip all over your bees. (Thermal expansion is a pain). So I designed my own version based on a cat waterer. There is the grid piece that fits into the feeder and sits on some posts to give the bees some dry footing above the sugar water so that they can't drown ( a problem with many bee feeders ).

I have provided two types of lid. The plexiglass version you need to cut and glue a piece of plexiglass on top of the printed piece. This gives you visibility into the feeder to watch your bees and at the same time doesn't allow venting. (I am currently going with single entrance non vented hives.). If you want it vented or can't source plexi there is a grid based top that has a 3d printed grid in the place of the plexiglass.

It has a 2" opening for the bees to come up and enter the feeder. I have just cut 2 " holes into. my inner covers and then bolted them down with M3 bolts or hot glued them on. I could design an adapter for the standard oval holes if you think that would be of help to you. I also use a feeding shim so that my inner cover isn't touching the jar, and random animals don't mess with it. I am told that in hive feeding is better as it is less likely to induce robbing than an entrance feeder. I also only feed my new hives that don't have honey supers on.

I suggest printing in PLA and then coating it in bees wax on all parts that the bees and syrup will be in contact with. I have put them on my hives with and without waxing them and the waxed ones are more quickly accepted by the bees. As you can probably tell from the pictures you punch an approximately 1cm hole in the mason jar and just plug it with your finger as you flip it over and put it in place.

The pictures are of my double nuc, and yes I know my inner covers are little too far from the tops of the frames. I am a beginner bee keeper and still figuring things out. This is the start of my second year, and this design I had working last year so I am feeling pretty happy with it.